Time is dependent on water pressure so there is really no set length of time to leave your sprinklers or system running. Put a rain gauge about half way between your sprinkler and the end of the arch the water stream reaches. Check the rain gauge periodically and when you find 1/2 inch of water in the gauge note how long the system has been running. You now know how long to water each area of your lawn.

The rule of thumb for watering lawns is 1/2 inch, twice per week. There are some variables however. If we have very dry weather patterns, plan to add a watering. Very light, sandy soil drains more quickly than heavier soils so an additional watering would be appropriate also. Take into account rainfall.